Citrus fruits contain a range of compounds which are biologically active in humans. Many of these compounds have a beneficial antioxidant activity with the ability to produce advantageous physiological effects in the treatment of conditions such as cancer, heart disease, high blood pressure and arthritis. For example citrus limonoid compounds derived from citrus may be used as anti-tumour agents. Further studies have also identified beneficial physiological effects produced by Flavonoids such as Flavanones and Polymethoxylated Flavones.
The bioactive compounds present in citrus fruits include groups consisting of Limonoids and Flavonoids.
Limonoids are a group of triterpenoid derivatives found in naturally occurring substances such as citrus fruits. The compounds which typically occur in citrus fruits are linked to a glucose molecule (the glucoside) and are commonly referred to as limonoid glucosides.
Flavonoids being to the group of benzopyrane derivatives which occur widely in nature. They have a typical chemical structure consisting of one benzene ring with a fused heterocyclic six membered ring containing an oxygen atom. These compounds also contain phenolic hydroxyl groups, which may be free, methylated or bound to sugars. Typically, flavonoids are distinguished by means of differences between the heterocyclic rings and between additional functional groups. Three types of flavonoids occur in citrus fruits—flavanones, flavones and flavonois. Many of these exist as glycosides.
Flavonones are the most predomonant type of citrus flavonoid. In fruits such as sweet orange, mandarin and lemon the dominant flavanone is the nearly tasteless hesperidin, while in more bitter fruits such as grapefruit, pummelo and sour orange, the more bitter flavanone naringin dominates.
The term polymethoxylated flavones represents the chemical family of flavones with a number of methoxyl groups equal to or greater than 4. These compounds are almost exclusively found in citrus fruits with a specific characteristic distribution for each variety. They are found in all parts of the fruit including the peel, flavedo, albedo and endocarp.
In the citrus processing industry, a commercial practice has arisen of producing juice or juice additives from citrus peel. In this process water soluble components are extracted from the peel using a range of devices. The resultant extract is typically bitter and astringent due to the large amounts of limonoid and flavonoid compounds which are particularly concentrated in the peel. To ensure the juice is not overly bitter the extract is typically clarified and de-bittered. The de-bittering process involves contacting the extract with a polymer adsorbent. This results in the adsorption on the polymer of some of the bitter principles; the remaining natural sugars, acids and some flavour compounds remain in the treated “juice”. This treatment results in the adsorption of a large portion of the flavonoid compounds in addition to the limonoids.
Commercial de-bittering operations typically regenerate the polymer by desorbing the removed compounds with a caustic soda solution. This process destroys the bioactive and flavour components resulting in their discharge as waste with the spent caustic solution, without harnessing these valuable bioactive by-products.
The object of the present invention is to address some or all of these problems, and to effect a separation of individual bioactive components.